Home-brew battery measuring station

[J57ltr]

Brian I have a 1F cap and some heatsink material I can donate to the cause. The second pic has 50W resistors on it so it should be perfect size for your setup. Also if you need I can make a fan shroud for it as well.

Jeff

[BrianG]

Originally Posted by J57ltr

Brian I have a 1F cap and some heatsink material I can donate to the cause. The second pic has 50W resistors on it so it should be perfect size for your setup. Also if you need I can make a fan shroud for it as well.

Jeff

Wow, I must have missed this post somehow! Didn't mean to ignore you.

Anyway; yeah, that would be awesome! Those heatsinks look like the PERFECT size. I intended to make the resistors lined up like you have in the pic, just a 46 more.

I got six 80mm fans for this project ($2 each at allelectronics.com), but was thinking I might put the fins side down, build a little tunnel, and put two fans (one at each end of the sink) and cool that way. This would allow an easy way to replace resistors if I blow some. Plus, it would look nice.

I also finished the power supply for the servo tester. I got a 12.6v/1A transformer from the same place. The supply actually has two outputs; one regulated for 8vDC for the servo tester (needs 6v-9v), and the other output is unregulated and puts out around 14vDC at ~750mA for the fans; perfect!

I was thinking a little though; To make this test repeatable, I'm gonna have some problems:

1) Constant current. The current through the resistors depends on voltage. I can program the ESC to output X amount of voltage, but as the battery depletes, the voltage will fall, and so will the current. So, testing a certain discharge rate (constant current) will be tough unless I constantly tweak the servo tester accordingly.

2) Pulse discharge profile. The servo tester I got has an automatic function which will sweep from min throttle to max throttle repeatedly. I can vary the speed of the sweep from slow to fast, but the profile is not "peaky" like we see in our cars. It starts at min throttle, ramps linearly up to max, sits there for a fraction of a second, ramps down linearly to the min, sits there for a fraction of a second, and the process repeats.

I wonder if I could see if Patrick will sell me one of those new ICE controllers he is using along with the custom software he is using?

[J57ltr]

That's exactly how I have done my heatsinks and it works great I just used 1 at the end that was a 4 5/8" square fan thermister controlled (ended up just shorting it out because it just wouldn't run fast enough for the application). Mainly a fan at 1 end because it's easier to bend. I have a ACAD pic I drew up but I can't remember how to capture a screen shot(edit: nevermind). I have it setup with 2 fans on 1 end.

As far as constant current you must add in the more parrallel resistance in order to keep the current constant. You could use a window comparator to turn on a fet or relay to switch in more resistors. I have a line on some .001 or .01 ohm resistors that are like 100W or 75W same style but bigger.

Jeff

[pinkpanda3310]

Have the MMM refurbs bought this project any closer to fruition